Characterization and Description of Anaeromyxobacter dehalogenans gen. nov., sp. nov., an Aryl-Halorespiring Facultative Anaerobic Myxobacterium

Abstract

Five strains were isolated which form a physiologically and phylogenetically coherent group of chlororespiring microorganisms and represent the first taxon in the Myxobacteria capable of anaerobic growth. The strains were enriched and isolated from various soils and sediments based on their ability to grow using acetate as an electron donor and 2-chlorophenol (2-CPh) as an electron acceptor. They are slender gram-negative rods with a bright red pigmentation that exhibit gliding motility and form spore-like structures. These unique chlororespiring myxobacteria also grow with 2,6-dichlorophenol, 2,5-dichlorophenol, 2-bromophenol, nitrate, fumarate, and oxygen as terminal electron acceptors, with optimal growth occurring at low concentrations (<1 mM) of electron acceptor. 2-CPh is reduced by all strains as an electron acceptor in preference to nitrate, which is reduced to ammonium. Acetate, H 2 , succinate, pyruvate, formate, and lactate were used as electron donors. None of the strains grew by fermentation. The 16S ribosomal DNA (rDNA) sequences of the five strains form a coherent cluster deeply branching within the family Myxococcaceae within the class Myxobacteria and are mostly closely associated with the Myxococcus subgroup. With the exception of anaerobic growth and lack of a characteristic fruiting body, these strains closely resemble previously characterized myxobacteria and therefore should be considered part of the Myxococcus subgroup. The anaerobic growth and 9.0% difference in 16S rDNA sequence from those of other myxobacterial genera are sufficient to place these strains in a new genus and species designated Anaeromyxobacter dehalogenans. The type strain is 2CP-1 (ATCC BAA-258).Myxobacteria have been considered obligately aerobic bacteria (26, 27). The phylogenic placement of this group within the delta-proteobacteria, however, would suggest the possibility of an ancestral anaerobic lifestyle for the myxobacteria (32). The delta-proteobacteria exhibit considerable anaerobic physiological diversity, including sulfate reduction, iron reduction, fermentation, and dehalogenation. Several dechlorinating bacteria in the delta-proteobacteria are able to utilize halogenated compounds as physiological electron acceptors for growth (1, 5, 9, 11, 14-16, 22, 29, 31, 38). Since there are many naturally occurring halogenated compounds in the environment (13) and chlororespiration releases considerable energy for growth (10), greater utilization of this lifestyle might be expected within the delta-proteobacteria.We used 2-chlorophenol (2-CPh) to search for chlororespiring anaerobes and found a novel group of myxobacteria, the first myxobacteria able to grow anaerobically. The new isolates grow using several ortho-substituted mono-and dichlorinated phenols, nitrate, and fumarate, as well as low concentrations of oxygen, as physiological electron acceptors. Four strains isolated from different environments in this study plus one previous isolate (5) allow a comprehensive characterization of the group. These strains ex...

Spatial structure of the microbial community in sandy carbonate sediment

“…6). Most of the deltaproteobacterial phylotypes from the 25 to 35 cm sample fall within the order Myxococcales, consisting of aerobic or facultatively anaerobic chemoorganotrophs (Sanford et al 2002). In contrast, deltaproteobacterial phylotypes from the 75 cm sample were related to the 'Desulfobacterales' or the 'Syntrophobacteraceae', which include anaerobic sulfatereducing and syntrophic organisms.…”

Biogeography and phylogenetic diversity of a cluster of exclusively marine myxobacteria

“…Myxobacteria have been known for a long time to produce spores (Shimkets, 1990;Shimkets et al, 2006), but in contrast to other organisms of the Deltaproteobacteria, most myxobacteria are strictly aerobic heterotrophs. A. dehalogenans (Cystobacterineae), however, was shown to be facultatively anaerobic, using acetate, H 2 , succinate, pyruvate, formate and lactate as electron donors, and various chlorophenolic compounds and nitrate as electron acceptors (Sanford et al, 2002). To elucidate how MMC bacteria survive in anoxic sediment, further studies are needed, that is, isolation of these organisms and subsequent physiological characterisation or molecular and gene expression analyses to investigate their metabolic activity.…”

Biodiversity of Dehalorespiring Bacteria with Special Emphasis on Polychlorinated Biphenyl/Dioxin Dechlorinators

“…The genus Anaeromyxobacter, which was described with the monotypic species Anaeromyxobacter dehalogenans (type strain: 2CP-1 T =ATCC BAA-258 T ) by Sanford et al 106) , is proposed for a group of facultatively anaerobic aryl-halorespiring myxobacteria. This organism is able to grow with chlorophenols as well as 2-bromophenol, nitrate, fumarate, and oxygen as terminal electron acceptors.…”